Parabola model

A very effective instrument for the analysis of the reactivity of the reactants is the intersecting parabolas model (IPM). This model was used in analysis of the activation... 

FIGURE 13.2 Correlation between electrophilicity index and EA of 54 neutral atoms and 55 simple molecules in the ground-state parabola model. (Reprinted from Parr, R.G., Szentpaly, L.V., and Liu, S.B., J. Am. Chem. Soc., 121, 1922, 1999. With permission.)... 

Kurz (1983) has attempted to correct this deficiency of Marcus theory by introducing a slight modification into the intersecting parabola model. Anti-... 

The electrophilicity index for, among others, the parent azete has been tabulated for two different models of the energy-electron number relationships <1999JA1922>. The electrophilicity index in the ground state parabola model and the electrophilicity index in the valance state parabola model tovs are reported as ajgs = tcvs/2 = 1.91. 

The intersecting parabolas model is consistent with the Hammond postulate that two states (such as reactant and transition structures) occurring consecutively in a reaction and having nearly the same energy content will involve interconversions with only a small reorganisation of the molecular structure. Consideration of Equation (11) reveals that for a... 

In the continuation of our discussion we face two tasks. First, we need to replace the simple two-parabola model described above by a realistic model that uses input from the energetic and dynamic properties of the solvent. Second, we have to provide a reliable description of the process that takes place when the electronic states become nearly degenerate, that is, of the electronic transition itself, taking into account the quantum mechanical nature of motion on two coupled potential energy surfaces. 

FIGURE 4.3 Tunneling paths for several vibrationally excited states in the case of the V-parabola model [Equation (4.16)]. Parameters are chosen to be (vibrational quantum numbers of I and s modes. (Taken from Reference [31] with permission.)... 

An extensive literature was devoted to polar effects in chemical reactions. The parabola model permits a fresh approach to this important problem. The introduction of a functional group into a hydrocarbon molecule alters the dissociation energy of the neighboring C—H bonds, which is indicated by the examples presented below. 

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